1. Field of the Invention
The invention relates to an anti-shake device, and more particularly to an anti-shake device for an optical instrument that provides positioning functions with a clamping manner.
2. Description of the Related Art
In a conventional anti-shake digital camera, a driving circuit drives a floating image-capturing unit to move at a high speed in two directions on a plane perpendicular to an optical axis, suppressing a blurred image or preventing a blurred image from occurring due to shakes during image capture, and further providing anti-shake functions.
Referring to FIG. 1 and FIG. 2, a conventional anti-shake device 1 is employed to quickly position an image-capturing unit A which has been moved at a high speed. The anti-shake device 1 comprises a cam 11, a transmission unit 12, a positioning member 13, and a torsion spring 14. The transmission unit 12 is connected to the cam 11. The positioning member 13 is abutted between the cam 11 and the image-capturing unit A. The torsion spring 14 is disposed on a fulcrum 131 of the positioning member 13. The transmission unit 12 drives the cam 11 to rotate, thereby driving the positioning member 13 to rotate between a fixing position and a separating position around the fulcrum 131. The torsion spring 14 persistently presses the positioning member 13 toward the image-capturing unit A, such that the positioning member 13 rotates in a curved way, similar to movement of a seesaw, around the fulcrum 131.
When the image-capturing unit A is positioned, the transmission unit 12 drives the cam 11 to rotate, shifting the positioning member 13 to the fixing position. The torsion spring 14 then presses the positioning member 13 to the image-capturing unit A, positioning the image-capturing unit A. On the contrary, when the image-capturing unit A is to move freely, the transmission unit 12 also drives the cam 11 to rotate, enabling the positioning member 13 to shift to the separating position in a clockwise way along a curved line B.
Nevertheless, the conventional anti-shake device 1 has the following drawbacks. As the positioning member 13 is displaced and rotated in a curved way, positioning deviation easily occurs. To suppress the positioning deviation, the manufacturing and assembly precision of the positioning member 13 must be enhanced, thus increasing manufacturing costs and assembly time of the anti-shake device 1. Moreover, because the positioning member 13 abuts only one side of the image-capturing unit A, the other side of the image-capturing unit A is easily raised, causing inclination of the image-capturing unit A. Thus, an imaging surface of the image-capturing unit A cannot be symmetrical to the optical axis, causing aberration of imaging. Additionally, as the positioning member 13 must securely press the image-capturing unit A, a high coefficient of elasticity is required for the torsion spring 14. Therefore, to effectively separate the positioning member 13 from the image-capturing unit A, a driving force from the transmission unit 12 must be increased, increasing consumption of electric power.
Hence, there is a need for an anti-shake device for an optical instrument with reduced manufacturing costs, aberration of imaging, and power consumption.